There are several reasons for brown spots on anthurium leaves.
Some of these are very serious, while others are minor issues that don’t pose any threat to your plant. Problems like overwatering or leaf spot diseases will need to be addressed quickly to ensure the long-term health of your plant.
Keep reading to learn the nine most common reasons for brown spots on anthurium leaves, as well as when you need to worry and what you can do to prevent them in the future.
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9 Causes Of Brown Spots On Anthurium Leaves
After keeping anthuriums for years at this point, I’ve just about seen every cause of brown spots that there is.
They can be summarised into 9 points, so let’s take a look at them all.
1. Sun Scorch
Exposing your anthurium to excess direct sunlight can cause sun scorch, leading to brown spots on the leaves.
This happens because intense sunlight causes an increased rate of loss of moisture from the leaves.
When this happens on one spot in particular, the roots are unable to provide moisture quickly enough to replace the moisture that is lost, leading to brown spots with yellow halos.
If you want more detail about sun-scorched anthuriums, check out our guide here.
2. Overwatering
Overwatering is a common cause of brown spots on anthurium leaves.
Anthuriums prefer moist but well-draining soil that suits their aerial roots. Too much water will suffocate the roots and can lead to root rot for two reasons:
- Dormant fungi like Phytophthora and Pythium become active in overwatered conditions.
- Roots that die due to suffocation will start to rot as they die, which then spreads to other roots.
If the roots are unable to transport nutrients and moisture to the leaves, they slowly die, turning yellow and developing yellow and brown spots in the process.
3. Wrong Soil Type
Using the incorrect soil type can affect your anthurium’s ability to retain or drain water properly.
Too much moisture retention can lead to root rot, as before with overwatering, causing browning on the leaves.
A lack of moisture will cause the leaves to develop brown spots and turn crispy.
4. Underwatering
While overwatering is detrimental, underwatering can also cause brown spots on anthurium leaves.
When the plant doesn’t receive enough water, leaves may become dehydrated and develop brown patches.
Dehydrated leaves will eventually die, and they will feel crispy to the touch, which is the main difference between underwatered and overwatered leaves.
5. Low Humidity
Anthuriums thrive in humid environments with humidity around 60 to 80%, and low humidity can lead to brown spots on the leaves.
This happens in a similar way to sun scorch – low humidity increases the rate of water loss from the leaves, which dries them out if the roots are unable to transport enough water to the leaves.
Brown spots on or around the tips of leaves are classic signs of low humidity.
6. Nutrient Deficiency
Nutrients are crucial for anthurium leaf development, as well as blooming, root growth, and overall development.
Nitrogen, for example, is responsible for chlorophyll production, which is vital for proper leaf growth and development.
Without enough nutrients, either from fertilizing or the potting mix, an anthurium will struggle to grow and show symptoms like brown and yellow spots on the leaves.
7. Pest Infestations
Pests, such as mites, mealybugs, and aphids, can cause brown spots on anthurium leaves as they feed on sap found within the plant leaves.
The damage they cause to the leaves not only causes brown spots and yellow spots, but they will also leave behind a honeydew residue as they feed, which promotes the growth of sooty mold as well.
8. Fungal Diseases
Root rot due to overwatering isn’t the only fungal disease that can affect anthuriums and cause brown spots on the leaves.
Bacterial wilt, for example, causes leaf yellowing followed by browning throughout the vascular system.
Brown spots can be observed around the veins of the plant, and brown slime may ooze out if the veins are cut.
9. Age
It’s completely natural for your anthurium to lose some leaves due to age every now and then.
Leaves that die naturally will turn yellow, usually from the edges, and this happens slowly.
Over time, brown spots will start to appear (as shown above), and eventually, the leaf will turn brown entirely and drop off.
Preventing Brown Spots On Anthurium Leaves
Ok, you can’t actually prevent brown spots on anthurium leaves completely.
Brown spots will always appear due to age, fluctuations in conditions, and other factors you can’t fully control.
You can definitely prevent brown spots due to problems like overwatering or sun scorch, however, and here are some tips for keeping brown spots to a minimum.
Pest Management
To effectively manage pests that may cause brown spots (and a host of other issues) on anthurium leaves, it is essential to regularly inspect your plants for any signs of infestation.
Should you encounter pests such as spider mites or aphids, remove them by rinsing them with water.
For more severe infestations, consider using an appropriate insecticide. This research by the University of Hawaii dives much deeper into the topic.
Disease Management
Disease management in anthuriums is critical to prevent brown spots and other related issues.
Ensure that your plant has proper air circulation, which helps prevent the development of diseases. Avoiding overwatering is crucial as well to prevent root rot.
If you notice signs of bacterial or fungal infections on your plant’s leaves, promptly remove the affected areas using sterilized pruning tools.
For a full disease breakdown with recommended control methods, I highly recommend this article by the University of Florida.
Adjusting Watering Practices
Watering an anthurium doesn’t have to be rocket science.
I like to water my anthurium when the top inch of soil dries out, and I use a layer of sphagnum moss above the soil to help retain moisture,
This helps to avoid overwatering and underwatering, therefore stopping brown spots as a result of these.
Providing Proper Lighting
Providing proper lighting is essential for anthurium care, as intense sunlight can cause brown spots on the leaves.
Place your plant in a bright location that receives indirect light, avoiding direct sunlight exposure.
Fertilizing Correctly
Fertilizing your anthurium is a great way to provide essential nutrients to help the leaves grow properly.
I usually fertilize once every one to two weeks during the summer, and much less frequently during the winter, with a dilute complete houseplant fertilizer.
Creating An Ideal Environment
The last thing to consider is the other care factors involved with keeping anthuriums.
Here’s a quick rundown of everything else to consider:
- Temperature – Provide temperature between 75°F and 90°F (roughly 23°C to 32°C) during the day and down to around 60°F (around 15°C) at night.
- Humidity – Keep the humidity high – around 50-80%. Consider using a pebble tray to boost the humidity or place your anthurium next to another plant.
- Well-draining soil mix – Make sure your soil mix drains water well whilst holding on to moisture. This will prevent overwatering and underwatering.
In Summary
Knowing what can cause brown spots on anthurium leaves is essential, as some reasons can be much more severe than others.
For example, if the leaves are showing brown spots due to overwatering, it’s important to inspect the roots and deal with any root rot before too much damage is done.
If sun scorch is to blame, on the other hand, all you need to do is adjust the position of your anthurium, and everything will be fine. It’s practically impossible to prevent all brown spots, but as long as they are not due to a serious problem, then it is completely normal.
If you want to learn more about this fascinating plant, you can check out some of our other articles below:
